It is generally known to provide a yarn supply creel extending in spaced parallel relationship along a false twist crimping machine to define a service aisle between the creel and the central frame of the machine. It is also known to direct the yarns from the yarn supply packages on the creel and along a path of travel above the service aisle while directing the yarns over yarn heating and cooling plates with the yarn heating and/or cooling plates forming a roof-shaped structure so that the thermal treatment zone is lengthened for the purpose of increasing the yarn processing speed without unduly increasing the machine height. False twist crimping machines of this general type are disclosed in U.S. Pat. Nos. 4,141,206, 4,058,961, and 4,572,458.
The thermal treatment zones extending across the service aisles, as disclosed in these prior art patents, do not provide an adequate length for the heating and cooling of the yarn in order to further increase the yarn processing speeds to more than 1,200 meters per minute. In order to be able to increase the operating speeds to this level, it has been found that an adequate length of the thermal treatment zone can be achieved only when a reliable contact of the advancing yarn with the yarn heating plate and the yarn cooling plate is insured.